页岩孔隙结构是控制与影响海相页岩储层质量的主要参数之一,对于页岩气资源评估、勘探和开发极其重要.为阐明泸州地区深层五峰-龙马溪组页岩孔隙结构,基于氦气膨胀法测孔隙度、矿物组分分析、TOC测试,采用CO2和N2吸附、高压压汞联合表征页岩全孔径,并与氧化-还原条件、水分、TOC等因素藕合,探讨页岩孔径分布的主控因素.结果表明:页岩中以介孔为主,微孔次之,宏孔较少,平均分别占总孔隙的73％、23％、4％;孔径分布与孔隙体积从五峰组向上先增加后降低;TOC与低孔径孔体积相关性高;水分占据页岩孔隙,大幅降低页岩孔隙体积和表比面积.因此,页岩孔径分布受沉积条件、TOC、水分共同控制.

选取泸州区块龙马溪组页岩为研究对象,基于核磁共振(nuclear magnetic resonance,NMR)实验、场发射扫描电子显微镜(field emission scanning electron microscope,FE-SEM)等手段,对泸州区块深层页岩的孔隙结构进行了分析,并利用分形几何近似方程计算了NMR分形维数,讨论了分形维数与总有机碳(total organic carbon,TOC)、热演化程度、矿物成分含量、孔隙度和渗透率等之间的关系.结果表明:泸州区块页岩广泛发育有机孔、粒间孔、粒内孔及微裂缝;有机孔孔径为 10～40 nm,无机孔孔径为 20～70 nm;NMR分形维数具有明显两段式特征,束缚流体孔隙分形维数(Dmin)与TOC、成熟度、石英含量呈正相关关系,与黏土矿物含量呈负相关关系,可动流体孔隙分形维数(Dmax)与石英含量、孔隙度、渗透率呈负相关关系.分形维数将矿物组分、储层物性与储层非均质性联系,研究结果可为深层页岩表征提供依据.

Organic matter (OM)-hosted pores are the primary pore type in the deep shale reservoirs of the Longmaxi Formation, in the Sichuan Basin, China, as well as the main locations for shale gas enrichment. However, the quantitative characteristics of OM pore space are not clear, and there is a lack of characterization methods. In this study, scanning electron microscopy (SEM), mercury intrusion porosimetry, low temperature gas adsorption, and logging data are all used to carry out multi-scale quantitative characterization of OM-hosted pores. The shape factor (F) model, fractal dimension model, and the OM porosity model are improved by combining them with mathematical morphology. The study primarily examines the effect of heterogeneity and the development of full scale pores in the OM pore space of the Luzhou area. The results show that (1) the ideal shape factor (F*) reflects the compaction degree of OM-hosted pores. From macropores to micropores, F* ranges from 0.61 to 0.93 as the shape gradually changes from flattened to round. (2) Shape factor and fractal dimension analyses revealed that the heterogeneity strength of the nanopore structure is mainly controlled by macropores. At the micro level and macro levels, the OM space shows lateral homogeneity and vertical heterogeneity. (3) Compared to the established method, the relative error of the improved model used in this study for predicting OM porosity was reduced by 19%. (4) Compaction and pore structure heterogeneity influence the formation of nanoscale pores in the Luzhou region and these factors also promote the development of mesopores and micropores, respectively. Furthermore, the OM porosities of the dominant shale reservoirs in Luzhou account for more than 50% of the overall porosity. This understanding will be of considerable benefit for evaluating deep shale reservoirs.

为分析鄂尔多斯盆地东缘山西组海陆过渡相页岩孔隙结构特征,以盆地内大宁—吉县地区D4井山西组10块样品为研究对象,基于有机地球化学测试、X-射线衍射(X-ray diffraction,XRD)实验、低温氮气吸附测试分析,运用孔隙分形研究方法探究鄂尔多斯盆地东缘山西组海陆过渡相页岩的分形维数与总有机碳(total organic carbon,TOC)、孔隙结构、矿物成分等之间的关系.结果 表明:鄂尔多斯盆地东缘山西组海陆过渡相页岩BET(Brunauer-Emmett-Teller)法测得的比表面积分布在2.39～16.72 m2/g,平均值为11.99 m2/g;BJH(Barrett-Joyner-Halenda)法测得的孔容分布在0.0110～0.0358 cm3/g,平均值为0.0243 cm3/g;平均孔径分布在9.19～18.46 nm,平均值为11.70 nm.研究区山西组页岩孔隙具有明显的分形特征,利用FHH(Frenkel-Halsey-Hill)模型计算的分形维数显示,样品在相对压力为0～0.45和0.45～1.00的吸附特征各异,可以得到分形维数D1和D2,其中D1表征页岩孔隙表面粗糙度,D2表征吸附孔结构不规则性;随着分形维数的增大,T OC和甲烷吸附量增大,石英质量分数、平均孔径和孔容减小;分形维数D1和D2均反映了鄂尔多斯盆地东缘山西组海陆过渡相页岩的吸附性能,而D2较D1对吸附性能的控制作用更大,表现为D2值与页岩吸附量相关性更强,且D2值增大时,页岩吸附量也呈明显的增加趋势.

以忠平1井乌拉力克组页岩为研究对象,应用二氧化碳和氮气吸附、高压压汞、氦气孔隙度、水平衡实验等方法,结合分形维理论表征和探讨页岩孔隙、孔径分布及其控制因素.研究结果表明:乌拉力克组页岩中微孔体积平均为0.00372 cm3/g,占总孔体积的20％;介孔体积平均为0.01186 cm3/g,占比为62％;宏孔体积平均为0.00333 cm3/g,占总孔隙的18％;页岩比表面积为14.47～21.81 cm2/g,微孔平均贡献67.92％比表面积,介孔31.93％,宏孔0.15％,直径<10 nm的孔隙贡献92.23％的比表面积;页岩微孔分形维数Dm为2.29～2.66,介孔分形维数D1为1.31～1.51,介孔分形维数D2为2.74～2.79.页岩孔体积和比表面积与黏土矿物和长石质量分数呈正相关,与石英质量分数呈负相关;水分降低孔体积和比表面积大约10％以上,水分和可溶沥青并存会降低储层孔隙和比表面积20％以上.因此,乌拉力克组页岩以介孔为主且孔隙非均质强,孔隙主要受矿物组分石英、长石、黏土矿物、水分与可溶沥青控制与影响.

为进一步探究煤储层孔隙结构特征对煤层气勘探开发的影响,以吐哈盆地沙尔湖煤田的煤样作为研究对象,基于显微组分分析、工业分析、低温液氮吸附实验和甲烷等温吸附实验的测试结果,利用Frenkel-Halsey-Hill(FHH)模型计算煤岩孔隙的分形维数,以期明确该地区煤岩的分形特征与含气性之间的相关关系.结果表明:吐哈盆地沙尔湖煤田煤岩的镜质组反射率(Ro)小于0.65％,属于低阶煤;采用FHH模型在相对压力分别为0～0.5和0.5～1.0的吸附特征差异得到分维数D1和D2,沙尔湖煤田煤岩的D1为2.505～2.680(平均值为2.578),D2为2.505～2.604(平均值为2.565),表明该煤田煤岩的孔隙表面较为粗糙,孔隙结构较复杂;D1与兰氏体积呈明显的正相关关系,与兰氏压力呈明显的负相关关系,而D2与兰氏体积、兰氏压力之间的相关性仍然不够明显.沙尔湖煤田煤岩孔隙结构的分布和孔隙类型同时影响着煤层气在煤体孔隙中的运移.

根据页岩样品不同孔径范围的累计孔体积与累计比表面积，结合焦页1井五峰-龙马溪组与慈页1井牛蹄塘组页岩样品的地球化学参数与岩样各矿物组分百分含量，分析页岩组分对两套地层孔隙发育差异的影响.结果显示，TOC与微孔呈正相关关系，表明有机质微孔对页岩孔隙发育提供了一定的贡献，五峰-龙马溪组页岩较牛蹄塘组更为发育有机质微孔.石英、黄铁矿含量与微孔的正相关关系表明，矿物支撑的原生孔与发育的边缘孔为页岩孔隙发育提供了有利贡献.石英与中孔、大孔的不同相关性表明石英根据其生物成因贡献的石英含量对中孔、大孔的保护程度不一.黄铁矿含量与大孔的正相关关系表明黄铁矿可以根据其含量的多寡为大孔提供一定程度的保护，长石与孔隙的负相关关系表明其对孔隙的支撑作用受到了压实作用、复杂构造的影响而不明显.碳酸盐矿物与孔隙的相关性不明显表示基于其较弱刚性、不稳的化学性质与较低含量未对孔隙发育产生明显影响.五峰-龙马溪组页岩较高的刚性矿物含量对储层矿物粒间孔、边缘孔等微孔与中孔、大孔的发育起到了较牛蹄塘组更为有利的影响.黏土矿物与微孔、中孔的负相关关系表明在较强压实作用下黏土矿物间孔隙易收缩，对储层孔隙发育产生不利影响，表明牛蹄塘组经历的更深历史埋藏对牛蹄塘组黏土矿物间孔隙发育起到了更加不利的影响.

In order to investigate the pore structure characteristics of coal reservoir which is in favor of the coalbed methane exploration and development, we explored the relationship between fractal dimension and pore diameter distribution, vitriolic reflectance, Langmuir volume and Langmuir pressure in low rank coal in Huhehu area of Hailar Basin. The results showed that the pores of low rank coal in Huhehu area of Hailar Basin have obvious fractal characteristics in different pore sizes. Compared with BET model, the fractal of FHH model is more consistent with the pore characteristics of low rank coal in Huhehu area. In FHH model, the adsorption characteristics of different macroscopic coal rock types are different at the relative pressure of 0 to 0.5 and 0.5 to 1.0, and the fractal dimensions D1 and D2 are obtained, where D1 represents the surface roughness of coal adsorption pore and D2 represents the irregularity of adsorption pore structure. The higher D2 is, the bigger the BET specific surface area product is, the higher the micropore content is, and the smaller the average pore diameter is. Both the fractal dimension D1 and D2 can reflect the adsorption performance of low rank coal in Huhehu area, and D1 phase plays a greater role in controlling the adsorption performance than D2.